Principles and Methods of Drug Administration

1. Principles and Methods of Drug Administration CHAPTER 3 -3 Dr. DipaBrahmbhatt VMD MpH dbrahmbhatt@vettechinstitute.edu

2. Parenteral vs. Non-Parenteral Administration Routes Parenteral Administration Non-Parenteral Routes Drugs given by mouth = Oral administration (PO) Rectally Sublingual • Literally means “administered in the space between the enteric canal (the GI tract) and the surface of the body”

3. Other Parenteral Administration Routes • Inhalation administration introduces drug to the animal by having it breathe the drug into the lungs • Particles diffuse across the alveolar membrane • Topical medication goes on the surface of skin or mucous membrane • Forms of topical medication are summarized in Table 3-2 in your textbook • Other parenteral administration routes are listed in Table 3-1 in your textbook

4. Route of Administration • Injectable / Parenteral • Local Routes • ‘Applied or given directly where the action of the drug is desired’ • Inhalation, topical (skin, eye, ear), other routes (rectal, vaginal, transdermal patches) • Oral Route

5. Method of administration: Breathing drug into respiratory tract INHALATION

6. Inhalation • Drugs are administered in the form of a gas/spray and are rapidly absorbed into the bloodstream. • An animal breathes in the drug > the lungs > alveoli where the particles diffuse into the bloodstream > distributed throughout the body Drugs inhaled are rapidly absorbed in the bloodstream

7. Inhalation • Gas Anesthesia (most common) • Drugs are volatilized (turned into gases) from liquids using a vaporizer • Treat respiratory conditions • Bronchodilators (anticholinergics), mucolytic enzymes, antibiotics, steroids • Drugs are nebulized (turned into a fine spray)

8. Topical • Dermatology (ear: drops, ointments and cream) and and ophthalmology (liquid drops and ophthalmic ointment) • Applied to the skin surface or mucous membranes • Forms: gel, ointment, cream, paste, liniment, lotion, powder, aerosol, or liquid drops • First dissolved and then diffused into the skin • Slowest route of absorption in the body as a whole • High concentration of drug locally, may be absorbed systemically

9. Topical • Localized skin infections/ allergies, abrasions • May be irritating, animal may chew/lick it off • Easy to administer • Can use drugs that otherwise would be toxic if injected • Have to shave fur for good contact • Other topical routes: nasal, rectal, vaginal

10. Topical • Solution: Clear liquid preparation, 1/more solutes and 1/more solvents • Solvent: the dissolving substance of a solution • Solute: the dissolved substance of a solution • Emulsion: A mixture of 2 immiscible liquids, one dispersed throughout the other in small droplets • Water – oil emulsion • Suspension: A finely divided, undissolved substance dispersed in water/oil. Liquid preparation that contains solid drug particles suspended in a suitable medium

11. FORMS OF TOPICALSDrug suspended in…. • Aerosols – solvent packaged under pressure • CREAM – water-oil emulsion • GEL– semisolid or jelly-like substance • Liniments – oily, soapy, or alcohol-based substance. Applied with friction • Lotions – liquid for dabbing, brushing, or dripping on skin without friction • OINTMENT – semisolid, lipid - based preparation that melts at body temp • PASTE – semisolid that retains its state at body temp • Powder – powder for external lubrication or absorption

12. Rectal Drug Administration • Alternative for delivering drugs: dangers presented to the vet staff / inability to administer the drug because of the animal’s condition • Usually much slower than oral drug absorption • Local irritation is a side effect of rectal drug therapy • Suppositories: melt/dissolve when inserted in body orifice

13. Vaginal Drug Administration • Therapeutic macromolecules • The rate and extent of absorption depends on • Drug formulation factors • Vaginal physiology • Age of the patient • Phase of the estrous cycle of the patient • Vaginal drug delivery systems include • Controlled internal drug release devices • Progesterone-releasing intravaginal devices • Vaginal sponges

14. Transdermal Drug Administration • Delivered through a patch on the skin • It passes from skin to bloodstream :drug to be delivered slowly and continuously (hrs/ days/ longer) • Skin irritation is one side effect • Only drugs needed in relatively small daily doses can be given through patches

16. Nonparenteral Administration Routes • Delivered directly to the GI tract • Most convenient (owner can do) • Before entering the bloodstream: oral drug must be released from the dose form, transported across the GI tract, and passed through the liver (reduces amount) • Long duration of activity, slow onset of action • Relatively safe (less likely for adverse effects) • No need for sterility • Gastric acid and disease may affect absorption rate • Ruminants have questionable absorption • Must get through GI mucosa

17. Oral Meds • Orally administered drug gets into bloodstream • Dissolving the drug form (solid / liquid) • Solid: tablet (sustained released, molded), capsule, powder, bolus, lozenges • Liquid: Solution, suspension, emulsion • Transport across GI tract • Drug passage through the liver

18. Oral Meds • Released from its form (tablet, capsule, liquid, powder, bolus, lozenges) after the animal swallows it • Tablets • Disintegrate in stomach liquid • Some tablets have an enteric coating (don’t break), meaning the drug does not dissolve (neutral/ alkaline pH) until it reaches the SI • They cause less stomach irritation

19. Oral Meds • Sustained released tablets • Coated so released in controlled fashion • Crystal of KCL on wax, microencapsulated drug (small drug particles with polymer coating) • Molded tablets • Soft, chewable • Mixed with lactose, sucrose, or dextrose and frequently a flavoring (Heartguard)

20. Oral Meds • Capsules • Gelatin shell (dissolves in stomach liquids) • Holds in the powdered or liquid medication • Boluses are large rectangular tablets used in large animals • Lozenges are in a hard, slow-release form. Not practical in animals (they will chew it) • Powders are dry and granulated and mixed with inert bulking and flavoring agents for dilution. These are easily mixed with food

21. Liquid Oral Drug • SOLUTIONS- drug is dissolved in liquid. Will not settle out if left standing (syrups, elixirs) • SUSPENSIONS- finely divided undissolved substance dispersed in water (shake the container to distribute) • EMULSION – fine droplets of oil in water or vice versa. Separate if standing for long periods of time. Must shake vigorously • All 3 can be mixed with food. Liquids don’t irritate the stomach as much as solid meds because they don’t settle out in a focal spot.

22. Liquid Oral Drug • Solutions, Suspensions and Emulsions • Mixed with food • Don’t irritate the stomach as much as solid meds because they don’t settle out in a focal spot • Not as accurate dose in food • Option for aggressive patient

23. Transport Across GI • Species anatomy can affect drug absorption • Ruminants • Longer to respond ( 3days) • Can be ineffective • Longer to reach therapeutic levels in blood • Horses: modified mono gastic, continuous grazers so some drugs absorbed rapidly others slowly • Monogastric

24. Liver After the drug is absorbed by the GI tract, it must pass through the liver. The liver affects blood levels because it can alter a drug. BE CAREFUL with drug choices when the liver is not functioning properly.

25. General Guidelines • Table 3-5: Pharmacological Aspects of Nursing Care

26. Therapeutic Range • Drug Factors • Route of administration • Drug dosage • Dosage interval

27. Dose DOSE = the amount of drug administered at one time to achieve the desired effect mL, cc, mg, Tablets

28. Drug Dose • LOADING DOSE – • the initial dose of a drug given to achieve drug levels in the therapeutic range in a short period of time • Large amount of drug initially / normal amount more often • MAINTENANCE DOSE – dose maintains drug in the therapeutic range • TOTAL DAILY DOSE – amount of drug given in 24 hours (ex: 1200 mg per day)

29. Drug Dosage • DOSAGE – amount of drug per animal’s body weight (ex: 5 mg/kg, 1g/lb, 60 mEq/kg ) • DOSAGE INTERVAL – how frequently the dosage is given (SID, BID, TID, Q24H, Q12H, Q8H, Q6H, QD, Q2D, PRN, etc) • DOSAGE REGIMEN (30mg/kg tid, po X 7 days) • Dosage • Dosage interval • Administration route • Duration of treatment

30. Drug Toxicity • Drug toxicity may be due to human error and/or accident • Drug toxicity may be related to side effects of the drug • Examples of drug toxicities: • Outright overdose • Relative overdose • Side effects • Accidental exposure • Interaction with other drugs • Incorrect treatment

31. Your patient is reacting to the medication, now what? • Directly remove the drug • Wash off the topicals, induce emesis for those ingested • Activated charcoal to bind what cannot be vomited • IV fluids to support the kidneys • Give an antidote if there is one • Provide care until the animal is through the toxicity

32. KEEP YOUR PATIENTS SAFE!